If you eat too much protein, does your body convert that into fat? Is there some nuance to this?
I think this is a common question regarding protein intake and its impact on energy balance, body weight, and body composition.
Assuming no other changes*, increasing dietary protein increases Calorie intake. The thermic effect of food, e.g. diet-induced energy expenditure, is higher in protein than other macronutrients. However, it is not sufficient to generally account for all additional Calorie intake and an energy surplus would be generated if starting from a maintenance level intake.
The body doesn’t really have a great way to turn protein into fat. Instead, the body will oxidize the protein as fuel and use other macronutrients for energy as needed. The rest will be stored as fat.
So, while increasing dietary protein is not going to lead to fat gain directly from protein, a large enough increase could increase body weight and body fat from carbohydrate and fat intake, where the additional protein is used as fuel.
*changing one aspect of nutrition generally has other knock-on effects, e.g. displacing other foods, changing energy intake, and so on. Most people will reduce or make no significant change to energy intake when increasing dietary protein from minimally processed sources.
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